1. Field of the Invention
The present invention relates to a front panel for use in a projection television receiver, a liquid crystal display, a plasma display, or the like. More particularly, the present invention relates to a front panel for a display which improves image contrast and color reproducibility of the display, and a front panel for a display which improves image contrast and color reproducibility of the display and further have a property preventing the troubles resulting from a near-infrared ray or an electromagnetic wave emitted from the plasma display.
2. Description of Related Art
In recent years, an improvement of image contrast and the ability to reproduce color with fidelity have been required of various display devices with a view to improving image quality. In terms of improving image quality, it has been known that the absorption of external light and the reduction of reflection leads to improved image contrast. It has also been known that the absorption of visible light other than red, green and blue emission spectra from an image light source by a front panel for a display is effective in improving image quality. In the plasma display, orange light emission spectra is known to exist in the vicinity of a wavelength of 580 nm other than the red, green and blue emission spectra. This light emission spectra degrades image contrast and color reproducibility of the display. In the plasma display, color reproducibility is poor because the intensities of red, green and blue emission spectra of the display are different each other.
To solve these problems, Japanese Examined Patent Publication No. 5-27098 discloses a transmission screen device wherein a colorant which absorbs light in the wavelength range of 500 to 600 nm and a compound exhibiting spectral properties having a maximum transmittance in the vicinity of a wavelength of 520 nm are blended in a transmission screen. In Japanese Unexamined Patent Publications Nos. 9-241520 and 10-128898, there is also disclosed a resin composite panel having a property absorbing selectively light in a specified wavelength range. This panel composes of a transparent resin and at least one light absorbing compounds having an absorbance of 0.01 or more in a specified wavelength range and has a total light transmittance of 50 to 90% and spectral light transmittances in the visible light wavelength range of 430 to 650 nm, which are: 60 to 85% in the range of 430 to 480 nm; 50 to 70% in the range of 530 to 580 nm; and 50 to 85% in the range of 590 to 640 nm. Further, WO98/23980 discloses a bandpass filter having, as additives, a plurality of dyes for improving image contrast of a color display.
In accordance with the methods disclosed in Japanese Examined Patent Publication No. 5-27098 and Japanese Unexamined Patent Publication Nos. 9-241520 and 10-128898, the degree of absorbing visible light other than the red, green and blue emission spectra is low and the effect of reducing the reflection of ambient light and improving image contrast is unsatisfactory. Moreover, there is no description of wavelengths and transmittances in WO98/23980 and the effect of improving image contrast and color reproducibility is unsatisfactory because of a high transmittance in the vicinity of a wavelength of 580 nm. Furthermore, the intensities of red, green and blue emission of the display cannot be corrected by any of the foregoing methods and an improvement in color reproducibility of the display is unsatisfactory.
Accordingly, an object of the present invention is to provide a front panel for a display which improves image contrast and color reproducibility of the display.
Another object of the present invention is to provide a front panel which improves image contrast and color reproducibility of the display and further has a near-infrared-ray absorbing ability.
To attain such objects, the present inventors have found, after thorough study, that a front panel for a display which improves image contrast and color reproducibility of the display is obtainable by adding light absorbing compounds to the front panel and thereby adjusting the light transmittance of the front panel at a wavelength of 450 nm to be higher than the light transmittance at a wavelength of 525 nm and adjusting the light transmittance of the front panel at a wavelength of 525 nm to be higher than the light transmittance at a wavelength of 630 nm and that a front panel for a display which improves image contrast and color reproducibility of the display and further having a near-infrared-ray absorbing ability is obtainable by further adjusting the mean light transmittance at wavelengths of 850 nm to 950 nm to 15% or less, and accomplished the present invention.
The present invention is as follows:
(1) A display front panel, wherein the light transmittance of the front panel at a wavelength of 450 nm is higher than the light transmittance at a wavelength of 525 nm and the light transmittance of the front panel at the wavelength of 525 nm is higher than the light transmittance at a wavelength of 630 nm;
(2) A display front panel recited in the foregoing item (1), wherein the transmittance of the front panel with respect to light emitted from a display is higher than the total light transmittance of the front panel;
(3) A display front panel recited in the forgoing item (1) or (2), wherein the light transmittance of the front panel at the wavelength of 490 nm is 80% or less, the light transmittance of the front panel at a wavelength of 580 nm is 60% or less, the light transmittance at a wavelength of 670 nm is 80% or less, and the total light transmittance is 40% or more;
(4) A front panel for a display recited in any one of the forgoing items (1) to (3), wherein the light transmittance at the wavelength of 580 nm is 60% or less.
(5) A display front panel recited in any one of the forgoing items (1) to (4), wherein the mean light transmittance at a wavelength of 850 to 950 nm is 15% or less; and
(6) A display front panel recited in any one of the forgoing items (1) to (5), wherein the front panel has at least one of a hardcoat layer, an electromagnetic-wave shielding layer, and an antireflection layer at a surface thereof or in the inside thereof.